1. Field of the Invention
The present invention relates to a display device, and more particularly, to an in-plane switching mode liquid crystal display (LCD) device and a method for manufacturing the same.
2. Discussion of the Related Art
A Cathode Ray Tube (CRT), one type of display devices, has been widely used for monitors of information terminals and measuring instruments including a television. However, it was difficult for the CRT to actively adapt to miniaturization and lightweight due to its weight and size.
A Liquid Crystal Display (LCD) device having a thin and small size has been actively developed in order to replace the CRT. Recently, the LCD device is used as a flat panel display device. Thus, demand for the LCD device has consistently increased.
In general, a low cost and high performance thin film transistor liquid crystal display (TFT-LCD) device uses an amorphous silicon thin film transistor as a switching device. At present, the LCD device is oriented towards a high resolution display that operates in a video graphic array (VGA) mode with the maximum resolution of 640×480 pixels, a super video graphic array (SVGA) mode of 800×600 pixels or in an extended video graphic array (XVGA) mode of 1024×768pixels.
Development and application of TFT-LCD industries have been accelerated in accordance with increase of the dimensions and increase of the resolution. To increase the productivity and ensure the low cost, many efforts have been continued in view of simplified process steps and improvement of yield.
However, in spite of the trend toward a large sized area of the TFT-LCD, a problem arises in that contrast ratio depends on a viewing angle. To solve this problem, various LCDs such as a twisted nematic LCD provided with a retardation film and a multi-domain LCD have been proposed. However, a problem still arises in that contrast ratio and color depend on a viewing angle.
To ensure a wide-viewing angle, an in-plane switching mode LCD device that controls alignment of a liquid crystal by an electric field parallel to a substrate has been proposed.
FIG. 1 is a plan view of a related art in-plane switching mode LCD device. FIG. 2 is a sectional view taken along line I-I′ of FIG. 1.
In the related art in-plane switching mode LCD device, as shown in FIG. 1 and FIG. 2, a gate line 1 is formed on a first substrate 10, and then a common line 3 is formed in parallel to the gate line 1. A common electrode 9 extends from the common line 3 to a pixel region.
In addition, a gate insulating film 12 is formed on an entire surface of the first substrate including the gate line 1, the common line 3, and the common electrode 9.
A data line 2 crosses the gate line 1 on the gate insulating film 12, so that a plurality of pixel regions are defined. For reference, FIG. 1 shows a unit pixel.
A thin film transistor (TFT) is formed on the gate insulating film 12 of a region where the gate line 1 crosses the date line 2. The TFT includes gate electrode, gate insulating film, semiconductor film, and source/drain electrodes.
A data electrode 8 is formed on the gate insulating film 12 within the pixel region. At this time, the data electrode 8 is arranged in parallel to the common electrode 9, and between the common electrodes 9. Also, the data electrode has an overlapping portion between the common line 3 and the common electrode 9 to form a storage capacitor. The data electrode 8 is connected with the drain electrode 7 of the TFT.
A passivation film 13 is formed on the gate insulating film 12 including the TFT, the data line 2, and the data electrode 8.
A color filter 21 is formed on a second substrate 20, and a liquid crystal layer 22 is formed between the first and second substrates 10 and 20.
Although not shown, polarizers are formed on external surfaces of the substrates 10 and 20 to polarize transmitted light, and alignment films adjacent to the liquid crystal layer are formed on internal surfaces of the substrates 10 and 20 to control an alignment direction of the liquid crystal layer.
A method for operating the related art in-plane switching mode LCD will be described in detail.
In the aforementioned related art in-plane switching mode LCD device, if a voltage is applied from an external driving circuit (not shown), an electric field parallel to the substrates 10 and 20 is generated between the data electrode 8 and the common electrode 9. A liquid crystal molecule aligned within the liquid crystal layer 22 is rotated along the electric field parallel to the substrates. As a result, an amount of light that passes through the liquid crystal layer 22 is controlled and gray scale is displayed in a state that the liquid crystal molecule is parallel to the substrate. For this reason, the difference of light transmittance depending on a viewing angle is reduced.
However, the related art in-plane switching mode LCD device has the following problems.
During the process, if the data line has an open region due to foreign particles, an extra repair line has to be installed by an additional process for repairing.
It is difficult to install the extra repair line. Even though the extra repair line is installed, the process is very complicated, thereby degrading reliability of the device.